1. Field of the Invention
The present invention relates to a rail welding device arranged for mobility along a track direction for effectuating the electric resistance welding of two track rails each of which comprises a rail web and a rail head. The rail welding device comprises a control unit, and two halves of the device spaced from each other and movable in the track direction, each half of the device being aligned with a respective one of the track rails and comprising a pair of clamping jaws pivotal towards and away from each other in a plane extending transversely to the track direction. Hydraulic cylinder means is provided for moving the two halves of the device in the track direction, and further hydraulic cylinder means pivot the clamping jaws of each half away from each other between a set-up position in which the rail heads of the track rails may freely pass between the clamping jaws and a welding position in which the clamping jaws engage the rail webs. In this way, sections of both rails of the track may be welded together.
2. Description of the Prior Art
Such devices for electric resistance butt-welding of track rails are well known, as disclosed, for example, in U.S. Pat. No. 3,349,216, British patent No. 2,185,703 and European patent No. 0 132 227.
European patent No. 0 253 634 discloses a rail welding device wherein sensors are built into the clamping jaws for detecting whether the rail section ends to be welded together are accurately aligned with each other horizontally and vertically. The correction of any misalignment is automatically initiated by suitable control signals.
It is the primary object of this invention to provide a rail welding device of the first-described type, which permits the welding to proceed with a greater margin of safety and dependability.
The above and other objects are accomplished in such a device according to the invention with a sensing device for detecting the welding position at the end of the pivoting motion of the clamping jaws and sending control signals required to effectuate the electric resistance welding to the control unit.
This sensing device makes it possible to determine in a simple and dependable manner whether the clamping jaws actually firmly engage and truly lock the rail webs between them before the hydraulic cylinder means moving the halves of the rail welding device in the track direction transmit the relative large tension and compression forces to the track rails. Mere observation of the clamping pressure does not guarantee a secure seating of the clamping jaws on the rails since such a pressure is also present when, for instance, there is a metallic obstruction between the rail web and the clamping jaws. With welding proceeding only in dependence on a control signal which guarantees the exact engagement of the clamping jaws with the rail webs, damage to the welding head resulting from an oblique positioning of the clamping jaws relative to the rails is securely obviated.